Why do some immigrant families in Germany struggle with integration after decades?

Disclaimer: I dont understand why but i have to censor when talking about a r a b s because the post got taken down??

Hello. I live in Germany and made a good friend last year who is A r a b. His family has been here for over 40 years but refuses to really integrate or connect with Germans or non-☪️ or people who arent from ME countries. Neither his parents nor his siblings (all in their 20s) have any German friends. What shocked me the most is that he has a girlfriend but told me he could never marry her because his family wouldn’t accept it. I’m trying not to be judgmental, but after learning this, I’ve started noticing more families like his. It’s frustrating because it feels disrespectful to the society they chose to live in, and it seems unfair to their kids, who are stuck in the middle. I feel bad for thinking this way, but it’s leaving a bad taste in my mouth. Why are they so stuck in their ways?